The present invention relates to a chemical amplifying type positive resist composition used in the micro processing of a semiconductor.
In general, a lithography process using a resist composition has been adopted in the micro processing of a semiconductor. In lithography, the resolution can be improved with a decrease in wavelength of the exposure light in principle as expressed by Rayleigh""s equation related to diffraction. A g-line with a wavelength of 436 nm, an i-line with a wavelength of 365 nm, and a KrF excimer laser with a wavelength of 248 nm have been serially adopted as exposure light sources for lithography used in the manufacture of semiconductors. Thus, the wavelength has become shorter year by year. An ArF excimer laser having a wavelength of 193 nm is considered to be promising as the next-generation exposure light source.
A lens used in an ArF excimer laser exposure machine or an exposure machine using a light source of shorter wave-length has a shorter lifetime as compared with lenses for conventional exposure light sources. Accordingly, the shorter time required for exposure to ArF excimer laser light is desirable. For this reason, it is necessary to enhance the sensitivity of a resist. Consequently, there has been used a so-called chemical amplifying type resist, which utilizes the catalytic action of an acid generated due to exposure, and contains a resin having a group cleavable by the acid.
It is known that, desirably, resins used in a resist for ArF excimer laser exposure have no aromatic ring in order to ensure the transmittance of the resist, but have an alicyclic ring in place of an aromatic ring in order to impart a dry etching resistance thereto. Various kinds of resins such as those described in Journal of Photopolymer Science and Technology, Vol. 9, No, 3, pages 387-398 (1996) by D. C. Hofer, are heretofore known as such resins. Also, as a resin in a resist for an ArF excimer laser lithography, an alternating copolymer consisting of polymeric units derived from alicyclic olefin and a polymeric unit derived from an unsaturated di-carboxylic acid anhydride (Proc. SPIE, Vol. 2724, pages 355-364 (1996) by T. I. Wallow et al), a polymer comprising polymeric units derived from alicyclic lactone (JP-A-2000-26446) and the like are known.
However, using such a conventional resin, balance among properties required for resist such as resolution, profile, sensitivity, dry-etching resistance and adhesion is insufficient, and further improvement has been desired.
An object of the present invention is to provide a positive resist composition of chemical amplification type which contains a resin component and an acid generating agent and is suitable for eximer laser lithography such as ArF laser lithography, KrF laser lithography and the like, wherein the composition is excellent in balance of properties such as resolution, profile, sensitivity, dry etching resistance, adhesion and the like.
The present inventors have previously found that adhesion to a substrate can be improved by using a resin having polymeric units of 2-alkyl-2-adamantyl (meth)acrylate, unsaturated dicarboxylic anhydride, alicyclic olefin and the like, or polymeric units of 2-alkyl-2-adamantyl (meth)acrylate, 3-hydroxy-1-adamantyl (meth)acrylate and the like, as a part of polymeric units in a resin constituting a chemical amplification type positive resist composition, and have suggested this finding (JP-A-11-305444 and 11-238542). Thereafter, the present inventors have further studied, and resultantly, found that a resist composition excellent in balance of properties such as resolution, profile, sensitivity, dry etching resistance, adhesion and the like can be obtained by using a resin having polymeric units such as an alicyclic lactone, unsaturated dicarboxylic anhydride, alicyclic olefin and the like, a resin having polymeric units such as an alicyclic lactone, 3-hydroxy-1-adamantyl (meth)acrylate and the like, or a resin having polymeric units such as an alicyclic lactone, (xcex1)xcex2-(meth)acryloyloxy-xcex3-butyrolactone and the like. Thus, the present invention was completed.
The present invention provides a practically excellent chemical amplification type positive resist composition comprising a resin which has the following polymeric units (A), (B) and (C), and is insoluble itself in an alkali, but becomes alkali-soluble by the action of an acid; and an acid generating agent.
(A): At least one polymeric unit of an alicyclic lactone selected from polymeric units represented by the following formulae (Ia) and (Ib); 
wherein, each of R1 and R2 independently represents hydrogen or methyl, and n represents a number of 1 to 3:
(B): At least one polymeric unit selected from a polymeric unit represented by the following formula (II), a polymeric unit of a combination of a unit represented by the following formula (III) and a unit derived from unsaturated dicarboxylic acid anhydride selected from maleic anhydride and itaconic anhydride and a polymeric unit represented by the following formula (IV): 
wherein, R3 and R7 represent hydrogen or methyl, R4 represents hydrogen or hydroxyl group, each of R5 and R6 independently represents hydrogen, alkyl having 1 to 3 carbon atom, hydroxyalkyl having 1 to 3 carbon atoms, carboxyl, cyano or group xe2x80x94COOR7 wherein R7 is an alcohol residue, or R5 and R6 together form a carboxylic anhydride residue represented by xe2x80x94C(xe2x95x90O)OC(xe2x95x90O)xe2x80x94;
(C) A polymeric unit which becomes alkali-soluble by cleavage of a part of groups by the action of an acid.
The resist composition of the present invention comprises a resin having the above-mentioned polymeric units (A), (B) and (C). As the monomer used for driving polymeric units of alicyclic lactones represented by the formula (Ia) and (Ib). specifically, (meth)acrylates of alicyclic lactones having a hydroxyl groups describer below, mixtures thereof, and the like are exemplified. These esters can be produced, for example, by reacting the corresponding alicyclic lactone having a hydroxyl group and (meth)acrylic acids (e.g., JP-A 2000-26446). 
Examples of monomers used for deriving the polymeric unit of formula (II) include 3-hydroxy-1-adamantyl acrylate, 3-hydroxy-1-adamantyl methacrylate, 3,5-dihydroxy-1-adamantyl acrylate and 3,5-dihydroxy-1-adamantyl methacrylate.
These monomers can be produced, for example, by reacting corresponding hydroxyl adamantans and (meth)acrylic acids (JP-A-63-33350).
R5 and R6 in the formula(III) each independently represent hydrogen, alkyl having 1 to 3 carbon atoms, hydroxyalkyl having 1 to 3 carbon atoms, carboxyl, cyano or a carboxylate residue represented by xe2x80x94COOR7 wherein R7 represents an alcohol residue. Alternatively, R5 and R6 may together form a carboxylic acid anhydride residue represented by xe2x80x94C(xe2x95x90O)OC(xe2x95x90O)xe2x80x94. Examples of the alkyl represented by R5 or R6 include methyl, ethyl and propyl. Examples of the hydroxyalkyl represented by R5 and R6 include hydroxymethyl and 2-hydroxyethyl. Examples of the alcohol residue represented by R7 include unsubstituted or substituted alkyl having about 1 to 8 carbon atoms and 2-oxoxolane-3- or -4-yl. Examples of the substituents of the substituted alkyl include hydroxyl and an alicyclic hydrocarbon residue. Specific examples of the carboxylate residue, xe2x80x94COOR7, represented by R5 and R6 include methoxycarbonyl, ethoxycarbonyl, 2-hydroxyethoxycarbonyl, tert-butoxycarbonyl, 2-oxoxolane-3-yloxycarbonyl, 2-oxoxolane-4-yloxycarbonyl, 1,1,2-trimethylpropoxycarbonyl, 1-cyclohexyl-1-methylethoxycarbonyl, 1-(4-methylcyclohexyl)-1-methylethoxycarbonyl, and 1-(1-adamantyl)-1-methylethoxycarbonyl.
Examples of monomers used for deriving the unit of formula (III) include 2-norbornene, 2-hydroxy-5-norbornene, 5-norbornene-2-carboxylic acid, methyl 5-norbornene-2-carboxylate, t-butyl 5-norbornene-2-carboxylate, 1-cyclohexyl-1-methylethyl 5-norbornene-2-carboxylate, 1-(4-methylcyclohexyl)-1-methylethyl 5-norbornene-2-carboxylate, 1-(4-hydroxylcyclohexyl)-1-methylethyl 5-norbornene-2-carboxylate, 1-methyl-1-(4-oxocyclohexyl)ethyl 5-norbornene-2-carboxylate, 1-(1-adamantyl)-1-methylethyl 5-norbornene-2-carboxylate, 1-methylcyclohexyl 5-norbornene-2-carboxylate, 2-methyl-2-adamantyl 5-norbornene-2-carboxylate, 2-ethyl-2-adamantyl 5-norbornene-2-carboxylate, 2-hydroxyl-1-ethyl 5-norbornene-2-carboxylate, 5-norbornene-2-methanol and 5-norbornene-2,3-dicarboxylic acid anhydride.
The derived from unsaturated dicarboxylic acid anhydride selected from maleic anhydride and itaconic anhydride is represented by the following formula (IV) or (V): 
Examples of monomers used for deriving the polymeric unit of formula (IV) include xcex1-acryloyloxy-xcex3-butyrolactone, xcex1-methacryloyloxy-xcex3-butyrolactone, xcex2-acryloyloxy-xcex3-butyrolactone and xcex2-methacryloyloxy-xcex3-butyrolactone. These monomers can be produced, for example, by reacting corresponding (xcex1)xcex2-hydroxy-xcex3-butyrolactone and (meth)acrylic acids.
Due to the change in solubility in alkali of the polymeric unit (C), the resin component which is alkali-insoluble or slightly soluble in alkali becomes alkali soluble.
Various kinds of carboxylic acid ester groups may be a group cleavable by the action of acid in polymeric unit (C). Examples of the carboxylic acid ester groups include alkyl esters having about 1 to 6 carbon atoms such as tert-butylester, acetal type esters such as methoxymethylester, ethoxymethylester, 1-ethoxyethylester, 1-isobutoxyethylester, 1-isopropoxyethylester, 1-ethoxypropylester, 1-(2-methoxyethoxy)ethylester, 1-(2-acetoxyethoxy)ethylester, 1-[2-(1-adamantyloxy)ethoxy]ethylester, 1-[2-(1-adamantancarbonyloxy)ethoxy]ethylester, tetrahydro-2-furylester and tetrahydro-2-pyranylester, 2-alkyl-2-adamantyl, 1-adamantyl-1-alkylalkyl and alicyclic ester such as isobornylester. Monomers used for deriving such the carboxylic acid ester groups may be acrylic type monomer, such as acrylate and methacrylate, alicyclic type monomers bonding to a carboxylic acid ester group, such as norbornene carboxylate, tricyclodecene carboxylic acid ester and tetracyclodecene carboxylic acid ester, and alicyclic acid esters in which an acrylic acid or a methacrylic acid and an alicyclic group form an ester group, such as those described in Journal of Photopolymer Science and Technology, vol.9, No. 3, pages 447-456 (1996) by Iwasa et al.
Among the monomers listed above, monomers having a bulky group containing an alicyclic ring such as 2-alkyl-2-adamantyl-, 1-adamantyl-1-alkylalkyl or the like are preferred since they give excellent resolution. Examples of the monomers having a bulky group include 2-alkyl-2-adamantyl (meth)acrylate, 1-adamantyl-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl 5-norbornene-2-carboxylate and 1-adamantyl-1-alkylalkyl5-norbornene-2-carboxylate. Particularly, 2-alkyl-2-adamantyl (meth)acrylate is preferred since it gives particularly good resolution. Representative examples of 2-alkyl-2-adamantyl (meth)acrylate include 2-methyl-2-adamantyl acrylate, 2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl acrylate, 2-ethyl-2-adamantyl methacrylate and 2-n-butyl-2-adamantyl acrylate. Among them, 2-ethyl-2-adamantyl (meth)acrylate gives good balance between sensitivity and heat resistance, and, therefore, particularly preferred.
As desired, another monomer having a group cleavable by the action of acid may be used together with the above monomer.
The resin component comprised in the resist composition of the present invention can be produced by a copolymerization of a monomer from which a polymeric unit (A) is derived, a monomer from which a polymeric unit (B) is derived, a monomer from which a polymeric unit (C) is derived and one or more optional monomers used if desired.
It is usually preferred that amount of the monomer from which a polymeric unit (A) is derived is 5 to 50% by mol, amount of the monomer from which a polymeric unit (B) is derived is 10 to 80% by mol and amount of the monomer from which a polymeric unit (C) is derived is 10% to 80% by mol based on total amount of the all monomers used in the copolymerization, although the preferable ranges may vary depending on the kind of radiation used for patterning exposure and the kind of the optional monomers used if desired. When alicyclic olefin unsaturated dicarboxylic acid anhydride are used for deriving a polymeric unit of a combination of a unit of formula (III) and a unit derived from unsaturated dicarboxyllc acid anhydride, they usually form an alternating copolymer.
It is advantageous that total amount of the monomer used for deriving the polymeric unit of formula (Ia) or (Ib), the monomer used for deriving the polymeric unit of formula (II), the monomer used for deriving the unit of formula (III), the monomer used for deriving the unit of unsaturated dicarboxylic acid anhydride and the monomer used for deriving the polymeric unit of formula (IV) is 20% by mol or more, more preferably 30% by mol or more, based on total amount of the all monomers including the optional monomers used in the copolymerization, even when other optional monomer is used.
The unit of formula (III) may be a polymeric unit which becomes alkali-soluble by cleavage of a part of groups by the action of an acid. In this case, the amount of the monomer used for deriving the polymeric unit (C) should be modified considering the amount of the unit of formula (III).
The copolymerization can be conducted according to a conventional method. For example, the resin (X) can be obtained by dissolving the monomers in an organic solvent, then conducting a polymerization reaction in the presence of a polymerization initiator, such as an azo compound. Examples of the azo compound include 2,2xe2x80x2-azobisisobutyronitrile and 2,2xe2x80x2-azobis(2-methylpropionate). It is advantageous that the reaction product is purified by re-precipitation or the like, after completion of the polymerization reaction.
The acid generating agent which is another component is decomposed to generate an acid by irradiating the component itself or a resist composition including the component with radioactive rays such as light and an electron beam. The acid generated from the acid generating agent acts on the resin to cleave the group which is to be cleaved by the action of an acid present in the resin. Examples of such acid generating agents include onium salt compounds, organic halogen compounds, sulfone compounds, and sulfonate compounds. Specifically, the following compounds can be mentioned: diphenyliodonium trifluoromethanesulfonate,
4-methoxyphenylphenyliodonium hexafluoroantimonate,
4-mthoxyphenylphenyliodonium trifluoromethanesulfonate,
bis(4-tert-butylphenyl)iodonium tetrafluoroborate,
bis(4-tert-butylphenyl)iodonium hexafluorophosphate,
bis(4-tert-butylphenyl)iodonium hexafluoroantimonate,
bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate,
triphenylsulfonium hexafluorophosphate,
triphenylsulfonium hexafluoroantimonate,
triphenylsulfonium trifluoromethanesulfonate,
4-methoxyphenyldiphenyl sulfonium hexafluoroantimonate;
4-methoxyphenyldiphenylsulfonium trifluoromethanesulfonate,
p-tolyldiphenylsulfonium trifluoromethanesulfonate,
p-tolyldiphenylsulfonium perfluorobutanesulfonte,
p-tolyldiphenylsulfonium perfluorooctanesulfonate,
2,4,6-trimethylphenyldiphenylsulfonium trifluoromethanesulfonate,
4-tert-butylphenyldiphenylsulfonium trifluoromethanesulfonate,
4-phenylthiophenyldiphenylsulfonium hexafluorophosphate,
4-phenylthiophenyldiphenylsuifonium hexafluoroantimonate,
1-(2-naphthoylmethyl)thiolanium hexafluoroantimonate,
1-(2-naphthoylmethyl)thiolanium trifluoromethane sulfonate,
4-hydroxy-1-naphthyldimethylsulfonium hexafluoroantimonate,
4-hydroxy-1-naphthyldimethylsulfonium trifluoromethanesulfonate,
2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine,
2,4,6-tris(trichloromethyl)-1,3,5-triazine,
2-phenyl-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(4-chlorophenyl)-4,6-bis(trichloromethyl)-1,3,5-triaizine,
2-(4-methoxyphenyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(4-methoxy-1-naphthyl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(benzo[d][1,3]dioxolane-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(3,4,5-trimethoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(3,4-dimethoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(2,4-dimethoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(2-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(4-butoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
2-(4-pentyloxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine,
diphenyl disulfone,
di-p-tolyl disulfone,
bis(phenylsulfonyl)diazomethane,
bis(4-chlorophenylsulfonyl)diazomethane,
bis(p-tolylsulfonyl)diazomethane,
bis(4-tert-butylphenylsulfonyl)diazomethane,
bis(2,4-xylylsulfonyl)diazomethane,
bis(cyclohexylsulfonyl)diazomethane,
(benzoyl)(phenylsulfonyl)diazomethane,
1-benzoyl-1-phenylmethyl p-toluenesulfonate (so-called benzointosylate),
2-benzoyl-2-hydroxy-2-phenylethyl p-toluenesulfonate (so-called xcex1-methylolbenzointosylate)
1,2,3-benzenetriyl trimethanesulfonate,
2,6-dinitrobenzyl p-toluenesulfonate,
2-nitrobenzyl p-toluenesulfonate,
4-nitrobenzyl p-toluenesulfonate,
N-(phenylsultonyloxy)succinimide,
N-(trifluoromethylsulfonyloxy)succinimide,
N-(trifluoromethylsulfonyloxy)phthalimide,
N-(trifluoromethylsulfonyloxy)-5-norbornene-2,3-dicarboxy imide,
N-(trifluoromethylsulfonyloxy)naphthalimide,
N-(10-camphorsulfonyloxy)naphthalimide, and the like.
It is also known that, generally in a chemical amplifying type positive resist composition, performance deterioration due to the deactivation of an acid associated with leaving after exposure can be reduced by adding basic compounds, especially basic nitrogen-containing organic compounds such as amines as quenchers. It is also preferable in the present invention that such basic compounds are added. Concrete examples of the basic compounds to be used as quenchers include the ones represented by the following formulae: 
wherein R11, R12 and R17 represent, independently each other, hydrogen, cycloalkyl, aryl or alkyl which may be optionally substituted with a hydroxyl, amino which may be optionally substitiuted with alkyl having 1 to 6 carbon atoms, or alkoxy having 1 to 6 carbon atoms; R13, R14 and R15, which are same or different from each other, represent hydrogen, cycloalkyl, aryl, alkoxy or alkyl which may be optionally substituted with a hydroxyl, amino which may be optionally substitiuted with alkyl having 1 to 6 carbon atoms, or alkoxy having 1 to 6 carbon atoms; R16 represents cycloalkyl or alkyl which may be optionally substituted with a hydroxyl, amino which may be optionally substitiuted with alkyl having 1 to 6 carbon atoms, or alkoxy having 1 to 6 carbon atoms; A represents alkylene, carbonyl, imino sulfide or disulfide. The alkyl represented by R11, to R17 and alkoxy represented by R13 to R15 may have about 1 to 6 carbon atoms. The cycloalkyl represented by R11 to R17 may have about 5 to 10 carbon atoms and the aryl represented by R11 to R15 and R17 may have about 6 to 10 carbon atoms. The alkylene represented by A may have about 1 to 6 carbon atoms and may be straight-chained or branched.
The resist composition of the present invention preferably contains the resin(X) in an amount in the range of 80 to 99.9% by weight, and the acid generating agent(Y) in an of 0.1 to 20% by weight based on the total amount of the resin(X) and the acid generating agent(Y). When a basic compound is used as a quencher, it is preferably contained in an amount in the range of 0.0001 to 0.1% by weight based on the total solid component weight of the resist composition. The composition may also contain, if required, various additives such as sensitizers, dissolution inhibitors, resins other than resin(X), surfactants, stabilizers, and dyes so far as the objets of the present invention is not harmed.
The resist composition of the present invention generally becomes a resist solution in the state in which the above-described components are dissolved in a solvent to be applied on a substrate such as a silicon wafer. The solvent herein used may be one which dissolves each component, has an appropriate drying rate, and provides a uniform and smooth coating after evaporation of the solvent, and can be one which is generally used in this field. Examples thereof include glycol ether esters such as ethylcellosolve acetate, methylcellosolve acetate, and propylene glycol monomethyl ether acetate; esters such as ethyl lactate, butyl acetate, amyl acetate, and ethyl pyruvate; ketones such as acetone, methyl isobutyl ketone, 2-heptanone, and cyclohexanone; and cyclic esters such as xcex3-butyrolactone. These solvents can be used alone or in combination of two or more thereof.
The resist film applied on a substrate, and dried is subjected to an exposure treatment for patterning. Then, after a heat-treatment for promoting a protecting deblocking reaction, development by an alkali developer is conducted. The alkali developer herein used can be various kinds of alkaline aqueous solutions used in this field. In general, an aqueous solution of tetramethylammoniumhydroxide or (2-hydroxyethyl)trimethylammoniumhydroxide (so-called colline) is often used.
The present invention will be described in more detail by way of examples, which should not be construed as limiting the scope of the present invention. All parts in examples are by weight unless otherwise stated. The weight-average molecular weight is a value determined from gel permeation chromatography using polystyrene as a reference standard.